1. Field of the Invention
The present invention relates to a fixing device of a copying machine or the like, and more particularly, it relates to an induction heating fixing device which includes a pressurizing means for applying pressure to a sheet of printing paper in a pressure contact area, through which the printing paper having a pattern of a magnetic toner transferred to a surface thereof is conveyed, and an induction heating means for induction heating the magnetic toner on the surface of the printing paper, which is being conveyed through the pressure contact area, so as to fix the pattern of the magnetic toner onto the surface of the printing paper.
2. Description of the Related Art
In known copying machines or the like, as disclosed in Japanese Patent Application Laid-Open No. 10-83883 for example, a fixing device operates to place a heating mechanism into contact with a toner, which formed into a pattern on a sheet of printing paper, so as to heat the toner, and at the same time, to apply pressure to the toner by means of a pressurizing mechanism, thereby fixing the toner to the printing paper. This technique uses a halogen lamp or the like for heating, but thermal efficiency thereof is not good. In recent years, there has been made a proposal for using a magnetic toner, which can be made to generate heat by itself under the action of a magnetic field, and hence has excellent thermal efficiency.
With the induction fixing device that carries out fixing by the use of the above-mentioned magnetic toner, thermal efficiency or the like is excellent and energy consumption can be suppressed to a low level, but the magnetic toner would be subjected to the influence of a magnetic field generated for induction heating, so that it can receive a force that causes it to move. Accordingly, there is a problem that it is not easy to reproduce a true image.
The present invention is intended to obviate the above-mentioned problem, and has for its object to provide an induction fixing device which uses a magnetic toner for image formation but is easy to reproduce a true image while preventing the magnetic toner from being moved even if influenced by a magnetic field generated for induction heating.
In order to solve the above-mentioned problem, the present invention resides in an induction heating fixing device including: a pressurizing means for applying pressure to a sheet of printing paper in a pressure contact area, through which the printing paper having a pattern of a magnetic toner transferred to a surface thereof is conveyed; and an induction heating means for induction heating the magnetic toner on the surface of the printing paper, which is being conveyed through the pressure contact area, so as to fix the pattern of the magnetic toner onto the surface of the printing paper. The pressure contact area is set to be broader than a range in which the magnetic toner on the surface of the printing paper is subjected to a force that causes it to move under the action of a magnetic field from the induction heating means.
With such an arrangement, the pressure contact area, through which the printing paper having the pattern of the magnetic toner is conveyed with the magnetic toner being fixed to the printing paper under the action of induction heating, is set to be broader than a range in which the magnetic toner receives a force that causes it to move under the influence of a magnetic field generated by the induction heating means. As a result, when the printing paper is conveyed to reach a place where the magnetic toner on the surface of the printing paper is subjected to a moving force (magnetic force) due to the magnetic field from the induction heating means, pressure has already been applied to the magnetic toner by the pressurizing means so as to prevent movement of the magnetic toner. Therefore, fixing of the magnetic toner is carried out without any movement thereof, thus making it possible to easily reproduce a true image.
Moreover, in this invention, the pressurizing means is formed of a non-conductive material which is not heated even if subjected to the magnetic field from the induction heating means. With this arrangement, it is possible to avoid consuming energy uselessly.
In addition, in the present invention, the pressurizing means includes a first and a second pressurizing belt of an endless belt configuration, and a pressurizing mechanism disposed in the first pressurizing belt. The second pressurizing belt is driven to rotate in a feeding direction while carrying the printing paper thereon. The first pressurizing belt is driven to rotate with the printing paper placed between the first and second pressurizing belts. The pressurizing mechanism applies pressure to the magnetic toner at least in the pressure contact area in such a manner that the magnetic toner on the surface of the printing paper placed between the first and second pressurizing belts is prevented from being moved under the action of the magnetic field from the induction heating means.
Further, in the present invention, the induction heating means is disposed in the second pressurizing belt in an opposed relation with the first and second pressurizing belts interposed therebetween.